1. Remove the batteries from your RTC
2. Connect your RCT to your (windows) computer via a Micro USB cable
3. Open the RCTupdatetoolENG program: The RCT should indicate: nbL
4. Click "select Software..." and select the file: RC55_xxxU_yyyy.rfp
5. Enable "BackToFactory at the end"
6. Click "load Software..."
7. Wait for popup: "loading-process finished successfully!" and click "Ok"
8. Disconnect cable
9. Put batteries in: during startup the installed version will be displayed shortly: xxx.U